Drum switch



Aug. 21, 1951 R. T. BASNETT DRUM SWITCH 2 Sheets-Sheet 1 Filed June 19, 1948 I INVENTOR Robert T. Busnefl.

III/[III I III] 7 WITNESSES:

BY PM if ATTORNEY 175,. i fii Aug. 21, 1951 R. T. BASNETT DRUM SWITCH 2 Shets-Sheet 2 Filed June 19, 1948 Fig.7.

INVENTOR Robert T. Busnefl ATTORNEY Patented Aug. 21, 1951 DRUM SWITCH Robert T. Basnett, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 19, 1948, Serial No. 33,950

16 Claims.

This invention relates to a drum switch of a type having a manually operable and rotatable indexing member which is movable angularly to different positions providing reversing or multiple speed connections for an electric motor.

More specifically, this invention relates to a drum switch generally of the type shown and described in my copending application, Serial No. 33,949, filed on June 19, 1948, and entitled Drum Switch, now abandoned.

In the above-mentioned copending application, there is shown a drum switch in which the contacts are positioned for circuit completing action by rotation of an operating member and in which contact-closing action is effected by an axial movement of the operating member with respect to its rotational positioning motion. The closing of the contacts by axial movement of the operating member on which they are mounted provides an improved action in drum-type switches as compared to conventionally constructed switches in which the contact closing action and force is applied entirely by a rotary movement of the movable contacts. It is necessary that the movable contacts be mounted on supports constructed of molded insulating material which is generally incapable of transmitting a torsional force. Consequently, conventional drum switches in which the contact closing action is effected by rotary motion require a complicated metallic reinforced operating mechanism for the movable contacts in which each of the mov able contacts is provided with a separate and individual insulating support. By effecting contact closure through an axial movement of the operating mechanism as described in the abovementioned application, the torsional forces produced by the rotational movement in efiecting contact closure in conventionally constructed drum switches are eliminated together with the resultant complicated operating mechanism required by such switches.

One of the principal objects of this invention is to provide a drum switch of the type shown and described in the above-mentioned copending application in which contact closure is effected by a substantially straight line movement of the closing contacts.

A further object is to provide an improved form of operating mechanism for opening the contacts of a drum switch with a snap action.

A still further object of this invention is to provide a novel form of mechanism for closing the contacts of a drum switch which is operable to position the contacts for closure by a rotary motion, and which is operable to close the contacts by a movement of the contacts which is in an axial direction with respect to their rotary positioning motion.

Other objects and advantages of this invention will become apparent from the following description.

In the drawing there is shown a preferred embodiment of the invention. In this showing:

Figure 1 is an elevational view of a drum switch, a part thereof being shown in section, constructed in accordance with the principles of this invention and showing the position of the operating parts when the switch is in its off position;

Fig. 2 is a vertical sectional view taken substantially along the line II-II of Fig. 1;

Fig. 3 is a sectional View taken substantially along the line III-III of Fig. 2;

Fig. 4 is a view, similar to Fig. 3, showing the operating parts in a different position;

Fig. 5 is a side elevational view looking from the right of Fig. 1;

Fig. 6 is a view, similar to Fig. 1, showing the position of the operating parts of the switch when it is in one of its operating positions; and

Fig. 7 is a sketch diagrammatically illustrating the various positions of the switch when connected to provide reversing and ofi connections for a three-phase alternating current electric motor.

In the drawing, the numeral l designates an insulating support having a horizontal base 2 and vertically extending sides 3 and 4. As best shown in Figs. 2 and 5, each of the sides 2 and 3 is provided with four openings 5 for the reception of conducting terminal connectors 6 having inwardly extending parts 1. Stationary contact elements 8 facing in an up direction are mounted on the inner ends of each of the inwardly extending terminal connector parts 1. As best shown in Fig. 5, only three of the openings 5 have terminal connectors mounted in position with respect thereto, the upper pair of connectors 6 being designated L2 and TI and the lower terminal connector being designated T3 for a purpose to be described. As best shown in Fig. 2, all four of the openings 5 in the side 3 have terminal connectors 6 mounted in position with respect thereto, the upper pair of terminal connectors being designated T2 and LI, and the lower pair of terminal connectors 6 being designated L3 and T3 for a purpose to be described.

As best shown in Fig. 2, an operating rod 9 is rotatably mounted on the support I in a position extending vertically and centrally thereof.

A manually operable and rotatable indexing member I!) is connected to the rod 53 by a sleeve in such fashion that rotational movement of the indexing member IE! will impart rotational movement to the rod 9.

An operating member 5 I constructed of molded insulatmgmaterial is provided with an opening I2 through which the rod 9 extends. The operating member II is rotatable independently of the rod 9 and its opening I2 is provided with an enlarged portion I3 in which is positioned a biasing spring IA. The spring is has one end bearing against a flange I5 at the upper end of the enlarged opening I 3 and its other end bearing against a flange I6 secured to the rod 9. The spring I4 is compressed to provide a biasing force for moving the operating member I I axially upward with respect to the rod 9 for a purpose to be described.

Movable bridging contacts ll, I3 and I9 formed of conducting material are connectedto supporting' lugs 20 formed on the operating member II by saddles 2| having springs for holding the movable bridging contacts in position thereon. The movable bridging contacts Ii, I8 and I9 are provided with contacts 23 at the ends thereof. The contacts as face in a downward and opposite direction With respect to' the stationary contacts 8 carried by the terminal connectors 5'.

To control the movement of the operating member I I and thereby the movement of the movable bridging contacts Ill, [8 and I9 carried thereby, there is provided a circular c'a'mm'ing member 24 which is positioned concentrically of and secured to the sleeve 53 for rotation there'- with in response to rotary movement of the indexing or controlrnember IE). The circular cam 24 is comprised of two cam'min'g parts 25 respectively havinga pair of arms 25 projecting in opposite directions and extending downwardly as best shown in Fig. 1 to provide angularly inclined camming surfaces 2?. The operating member I I is provided with parts 23 extending outwardly therefrom at diametrically opposite points to provide supports for a pair of rollers 29. Each of the rollers 29 is a cam follower and is engageable with the camming surfaces 2? provided by one of the (Jamming parts 25. The bias provided by the spring I 4 operates to maintain the cam followe'rs or rollers 29 in engagement with the camming surfaces 27.

The manually operable indexing or control member I 0 has a central off position from which it is movable in opposite angular directions through an angle of substantially 90 to operating positions designated as forward and reverse in Fig.- '7. When the control member Ill is in its central or off position, the cammin'g parts 25 extend substantially transversely with respect to the sides and 4 of the support I. Vfith the camining parts 25 so arranged, the axial bias on the operating member I I will force the rollers 29 upwardly' to the apex of the diverging cammihg surfaces 27 as viewed in Fig. 1 to position the operating member II with respect to its control member 'Il). In this position of the operating member II, the movable bridging contact members I1, [8 and I9 are inclined at an angle of 45 with respect to the sides 3 and 4. Rotation of the operating member I i through an angle of 45 in either direction from the position shown in Fig. 1 will be operative to rotatably position the contacts 23 carried by the bridging contact elements I7, I8 and I9 for engagement with the contacts 8 carried by the terminal connectors 6 in a manner to be described. However, it will be noted that when the operating member II is rotated through an angle of 45 from the position shown in Fig. l, the contacts 23 will be spaced axially from the stationary contacts 8.

To rotatably position the operating member II as described above, it is merely necessary to rotate the: control member Ii) through an angle of 45 in either direction from the position shown in Fig. 1. During this movement, the bias of the spring I4 on the operating member I I is effective to maintain the cam followers 29 positioned in the apexof the cam surfaces 21, and the operating member I] will be rotated with the control member I0. When the operating member II is moved through an angle of 45, a corner 30 of the part 28 will move into engagement with the sides of the support I as at 35 in Fig. 4. The sides of the support I thus constitute a stop limitingrotational movement of the operating member Il. Continued rotation of the control member II! to its operating position will cause the cam-' ming elements 25 to be rotated relatively to the cam followers 29 and operating member II. During this final movement, the downwardly extending cam surfaces 27 on the arms 26 will be effective to cam the operating member II downwardly against the bias of its spring M to engage the contacts 23 with the contacts 8. As contact engagement is thus effected, the operating member I I will be latched in its downward position by means of a ledge 32 on the part 28 moving underneath a latching ledge 33 formed on the support I. The outer ends of each of the camming parts 26 are provided with hooks M for forcing the latching ledge 32 to a position underneath the latching ledge 33. The manner in which the hooks 34 engage with the parts 38 is best shown in Fig. 6. The latching ledges 32 and 33 will be maintained inter-engaged by the biasing force applied in an upward direction to the operating member II by the spring M.

To effect the final movement of the operating member I8 into its operating position with a snap action and thereby engagement of the contacts 8 and 23 with a snap action, there is provided snap acting mechanism which will be best understood by referring to Figs. 3 and 4. The snap acting mechanism comprises a camming member 3'! connected to the sleeve M for rota tion therewith in response to rotation of the control member Iii. The cam 3 is provided with a pair of pointed projections 33 so shaped to provide angularly inclined and outwardly projecting camming surfaces 39 terminating at a point M] from which camming surfaces H extend inwardly toward the sleeve 5! A cam follower or roller 42 is carried by a spring 53 which provides a bias for moving the roller 2-2 inwardly toward the sleeve 5!. When the control member I l is in the off position, the parts are so arranged that the roller 42 is positioned in the apex of the angularly inclined camming surfaces as. Upon I rotation of the sleeve 5| in response to rotation of the control member Iii, the roller 52 will be moved outwardly by the camming surfaces 3?? and the twist of the spring 63 will be increased. When the parts are moved through an angle of 45, they will be in the position as shown in Fig. 4 in which one of the points ill will be aligned with the center of the roller 42 and the center of the sleeve 5|. As the movement is continued beyond 45, the roller 42 will move onto the cam surface II, and the inward bias provided by the spring 43 will be applied in a direction to assist the rotation of the control member ID to its 90 operating position. This latter movement, due to the force applied by the spring 43, will take place with a snap action and the contacts will thus be engaged with a snap action.

It will be recalled that when the control member moves into one of its operating positions to effect contact closure, the operating member H is latched against axial upward movement by the biasing spring 14 by the latching interengagement of the ledges 32 and 33. When the control member 10 is moved from one of its operating positions to its off position, no movement will be imparted initially to the operating member H by reason of the latching inter-engagement of the ledges 32 and 33. This latching inter-engagement of the ledges 32 and 33 will be maintained until such time as the control member It moves substantially into its off position. As the control member ID moves to a position adjacent its off position, the hooks or latch actuators 34 will move into engagement with the parts 28 to rotate the ledge 32 out of engagement with the ledge 33. As soon as the latching ledges 32 and 33 are disengaged, the bias provided by the spring 14 will operate to move the operating member ll upwardly to disengage the contacts 23 with respect to the contacts 8. As the operating member ll moves upwardly, the rollers 29 will move into engagement with the camming surfaces 21 which will function to rotate the operating member H to the position shown in Fig. 1 as the operating member I! moves upwardly under the influence of the biasing spring 14. The manner in which the latch actuator 34 operates to effect an unlatching action provides an advantage with respect to breaking the contact engagement in the event that the contacts have sealed together during the time in which they are in closed position. If the contacts have sealed by welding, the force applied. by the latch actuator 34 to the part 28 is in a direction tending to break the welding seal and release the operating member H for axial movement by its biasing spring.

The latch actuators or hooks 34 are provided at the ends of each of the camming arms 26 and operate alternately in cooperation with the parts 28 on the operating member H to effect first a latching action and second an unlatching action. The alternate operation will be best understood by considering the operation of the two visible arms 26 and the part 28 in Fig. 1. As the member 13 is rotated clockwise to an operating position, the hook 34 on the cam arm 23 to the right as viewed in Fig. 1 will engage with the part 28 to effect a latching action. As the control member In is moved in a counterclockwise direction to its off position, the hook 34 on the cam arm 25 to the left as viewed in Fig. 1 will engage with the part 28 to effect an unlatching action. Similarly, when the control member I0 is rotated counterclockwise to an operating position, the hook 34 on the arm 26 to the left will effect the latching action, and on return movement of the member ID, the hook 34 on the arm 25 to the right will effect the unlatching action.

Attention is invited to the fact that the return movement of the operating member ID to its off position is accomplished with a snap action by reason of a snap acting mechanism comprising the camming member 31 and biasing spring 43. As the control member ID is moved from one of its operating positions toward its off position, the camming surface 4| will move the roller 42 outwardly against the action of its biasing spring 43. When the cam member 31 passes its position as shown in Fig. 4, the roller 42 will move into engagement with the camming surface 39, and the bias provided by the spring 43 will be effective to complete the movement of the control member ID to its off position with a snap action.

The specific manner in which the contacts are arranged provides an advantage in that the overall length of the switch is decreased. This is accomplished by having the contact bridging elements l1 and i8 arranged in a common plane rather than in a plane separated from each other in accordance with common practice.

The manner in which the reversing connections for an electric motor are completed by the bridging contact elements [1, l8 and I9 will be readily apparent from an examination of the diagrammatic showing of Fig. 7 in which the leads connected to terminals Tl, T2 and T3 represent the terminal connections to an electric motor and the leads connected to terminals Ll, L2 and L3 represent the line connections to a polyphase three-phase source of alternating current.

From the foregoing, it will be noted that the cam 24 and cam follower-rollers 29 provide an over-running connection between the control member I0 and operating member ll by which rotation of the control member I0 is effective during a portion of its movement to impart rotation to the operating member H for positioning the movable contacts 23 for engagement with the stationary contacts 8. Attention is particularly invited to the fact that, by reason of this over-running connection, the operating member II is rotatable independently of rotation of the control member [0. Attention is further invited to the fact that rotation of the control member In is effective to operate the switch by two movements independent of each other which involve a rotative positioning movement of the operating member H and an axially contact closing movement of the operating member I I. It will be particularly noted that contact closing action is effected by a substantially straight-line movement of the operating member H without any rotative movement being imparted thereto. It will also be noted that the mechanism operates to effect such closing action with a snap-action.

Since certain changes may be made in the above-described construction and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all the matter contained in the above description and shown in the accompanying drawing shall be considered as illustrative and not in a limiting sense.

I claim as my invention:

1. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member operable upon rotation of said control member through a given angle from a neutral position to rotate said operating member to position said contact bridging elements in registry for engage" ment with said stationary contacts, cam means coupled to the control member and operable on said operating member upon rotation of said control member through a greater angle than said given angle to move said operating member axially to effect contact engagement between said contact bridging elements and stationary contacts, and a latch operable in response to the axial movement of said operating member for latching said operating member against axial movement out of contact engaging position.

2. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member operable upon rotation of said control member through a given angle from a neutral position to, rotate said operating member to position said contact bridging elements in registry for engagementwith said stationary contacts, cam means coupled to the control member and operable on the operating member upon rotation of said control member through a greater angle than said given angle to move said operating member axially to effect contact engagement between said contact bridging elements and stationary contacts, a latch operable in response to the axial movement of said operating member for latching said operating member against axial movement out of contact engaging position, and a latch actuator rotatable with said control member for releasing said latch upon rotation of said control member in a direction toward said given position.

3 An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member operable upon rotation of said control member a predetermined angular distance from a predetermined position to rotate said operating member to position said contact bridging elements in registry for engagement with said stationary contacts, and upon rotation of said control member beyond said predetermined angular distance to move said operating member axially to effect contact engagement between said contact bridging elements and stationary contacts, and a snap acting device for eifecting the rotational movement of said control member beyond said predetermined angular distance with a snap action.

4. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member operable upon rotation of said control member a predetermined angular distance from a predetermined position to rotate said operating member to position said contact bridging elements in registry for engagement with said stationary contacts, cam means coupled to the control member and operable on the operating member upon rotation of said control member beyond said predetermined angular distance to move said operating member axially to efiect contact engagement between said contact bridging elements and stationary contacts, a snap acting device for effecting the rotational movement of said control member beyond said predetermined angular distance with a snap action to thereby engage said stationary contacts and contact bridging elements with a snap action, and a latch operable in response to the axial movement of said operating member to engage said contacts for latching said operating member against axial movement out of contact engaging position.

5. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member operable upon rotation of said control member through a given angle from a neutral position to rotate said operating member to position said contact bridging elements in registry for engagement with said stationary contacts, cam means coupled to the control member and operable on said operating member upon rotation of said control member through a greater angle than said given angle to move said operating member axially to effect contact engagement between said contact bridging elements and stationary contacts, a snap acting device for effecting the rotational movement of said control member from the given angle to its final position with a snap action to thereby engage said stationary contacts and contact bridging elements with a snap action, a latch operable in response to the axial movement of said operating member for latching said operating member against axial movement, and a latch actuator operable in response to return movement of said control member toward said neutral position to unlatch said operating member for return of axial movement.

6. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member, said rotatable control member having an off position and an operating position, said overrunning connection being operable upon rotation of said control member through a given angle from its off position to position said contact bridging elements in registry with the stationary contacts, cam means coupled to the control member and operable on the operating member upon rotation of the control member from the given angular position to its operating position to move said operating member axially to effect contact engagement between said stationary contacts and contact bridging elements, a latch operable in response to axial movement of said operating member for latching said operating member against movement out of such position, and a latch releasing actuator rotatable with said control member and engageable with said latch to release said operating member for movement to its oif position.

'7. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between said control member and operating member, said rotatable control member having an off position and an operating position, said overrunning connection being operable upon rotation of said control member through a given angle from its off position to position said contact bridging elements in registry with the stationary contacts,

cam means coupled to the control mmeber and operable on the operating member upon rotation of the control member from the said given angular position to its operating position to move said operating member axially to effect contact engagement of the contact bridging elements with said stationary contacts, there being substantially no rotational movement imparted to said operating member during the final rotation of said control member, and a snap acting device for effecting the final rotation of said control member and thereby axial movement of said operating member with a snap action.

8. In an electric switch, a support, an electrical contact operating member mounted for rotational and axial movement on said support and having a bias for axial movement in one axial direction, a control member mounted on said support for rotational movement independently of said operating member, said control member being movable in angularly opposite directions from an off position to either of two operating positions, a cam connected to said control member for rotation therewith, and a cam follower mounted on said operating member, the axial bias on said operating member being operative to maintain said follower in engagement with said cam to provide a connection operable to rotate said operating member a predetermined angular distance in response to rotation of said control member an equal angular distance from its off position, said cam being movable relative to said follower in response to rotation of said control member beyond said predetermined angular distance into one of its operating positions, said cam having a shape effective in response to said relative movement to move said operating member axially against its bias to a contact operating position.

QTIn an electric switch, a support, an electrical contact operating member mounted for rotational and axial movement on said support, a control member mounted on said support for rotational movement independently of said operating member, said control member being movable in angularly opposite directions from an off position to either of two operating positions, a cam connected to said control member for rotation therewith, a cam follower mounted on said operating member, said operating member having a bias for axial movement in a direction to maintain said follower engaged with said cam, the engagement of said follower and cam providing a connection by which rotation of said control member from its off position will impart rotation to said operating member, and a stop on said operating member engageable with said support for limiting its rotation with respect thereto, said cam having a surface rotatable relative to said follower in response to final rotation of said operating member to an operating position after operation of said stop for moving said operating member axially against its bias to a contact operating position.

10. In an electric switch, a support, an electrical contact operating member mounted for rotational and axial movement on said support, a control member mounted on said support for rotational movement independently of said operating member, said control member being movable in angularly opposite directions from an off position to either of two operating positions, a cam connected to said control member for rotation therewith, a cam follower mounted on said operating member, said operating member having a bias for axial movement in a direction to maintain said follower engaged with said cam, the engagement of said follower and cam providing a connection by which rotation of said control member from its off position will impart rotation to said operating member, a stop on said operating member engageable with said support for limiting its rotation with respect thereto, said cam having a surface rotatable relative to said follower in response to final rotation of said operating member to an operating position after operation of said stop for moving said operating member axially against its bias to a contact operating position, and a latch responsive to axial movement of said operating member to an operating position for latching it against axial movement by its bias out of said position.

11. In an electric switch, a support, an electrical contact operating member mounted for rotational and axial movement on said support, a control member mountedon said support for rotational movement independently of said operating member, said control member being movable in angularly opposite directions from an off position to either of two operating positions, a cam connected to said control member for rotation therewith, a cam follower mounted on said operating member, said operating member having a bias for axial movement in a direction to maintain said follower engaged with said cam, the engagement of said follower and cam providing a connection by which rotation of said control member from its off position will impart r0- tation to said operating member, a stop on said operating member engageable with said support for limiting its rotation with respect thereto, said cam having a surface rotatable relative to said follower in response to final rotation of said operating member to an operating position after operation of said stop for moving said operating member axially against its bias to a contact operating position, and a snap acting device for effecting the final rotation of said control member with a snap action.

12. In electric switching means, the combination of, a support, an operating member of insulating material mounted for rotational, and axial movement on said support, said operating member having a neutral position and two operating positions, two pairs of stationary contacts mounted fixedly on said support, a contact bridging element mounted on said operating member, a rotatable control member, a coupling for coupling said control member to the operating member, said coupling comprising an over-running connection between said control member and said operating member to effect a rotation of the operating member upon rotation of the control member to selectively position the contact bridging element over one pair of stationary contacts or the other pair of stationary contacts depend ing on the direction of movement to selected angular positions of the control member from its neutral position, and cam means coupled to the control member operable in response to rotation of said control member beyond said selected angular positions to move said operating member axially to cause the contact bridging element to .bridge the particular pair of stationary contacts above which the contact bridging element is positioned by the initial angular movement of the control member to a selected position.

18. In electric switching means, the combination of, a support, an operating member of insulating material mounted for rotational and member having la neutral position and two operating positions, pairs of stationary .contacts mounted fixedly on 'saidsupport, a contact bridging element mounted on said operatingmember,

a rotatable control member, a coupling for coupling said control member 'to the operating member, said coupling comprising an over-running connection between said control member and said "operating member to feifect a rotation of the operating member upon rotation of the control memb er'to selectiv'lyposition the contact bridging element over one pair of stationary contacts 'orthe other pair of stationary contacts depending 'on the direction of movement to selected angularpositions'of'the control member from its neutral position, cam means coupled to the control member operable in response .to rotation of said control member beyond said selected angula'r positions to move said operating member axially'to cause the'contact bridging element to bridge 'the'par'ticular pair of stationary contacts above which the contact'bridging elementis positioned by the initial angular movement of the control member to a selected position, second cam means, a spring biased member engaging the second cam means for effecting the axial movement 'oftheoperating member with a snap action.

14.'In electric switching means, the combination of, a support, an operating member of insulating material mounted for rotational and axial movement on said support, said operating membenhavinga-neutral position and two operating positions, two .pairs of stationary contacts mounted fixedly on said supporta contact bridg-' 'ing element said operating member, a rotatable control member, a couplingfor coupling said control-member to the operating member, said coupling comprising an over-running "connection between s'aid control member and said operating memberto effect a rotation of the operating memberupon rotation of the control member to selectively position the contact bridging element over one lpair of stationary contacts or the otherpairof stationary contacts depending on the direction of movement to selected angular-positions of the control member from its neutral position,cam means coupled to the control member operable in responseto rotation of said control member beyondsaid selected angular positions to move said operating-member axially to caus e the contact bridging element to bridge the particular pair of stationary contacts above which the-.contact bridging element is positioned by the initial "angular movement of the control member to one of its selected positions, second cam means, a spring biased member engaging the second cam means, for effecting the axial movement of the operating member with a snap action, and latching means actuated by the first cam means for latching the operating member .into its final operating position.

15. In electric switching means, the combination of, a support, a pair-of "spaced stationary contacts carriedby saidrsupporaan operating member mounted for rotational and axial movement on said support, a'contact bridging elementcarried by said operating member, a coupling .for coupling said .control..member to the operating member, said coupling comprising an over-runningconnection between said control member and operating member operable upon rotationof said control "member a predetermined angular distance from a givenposition to'rotate said'opcrating member to position said contact bridging element in registry for engagement with said two stationary contacts, and .cam mean actuated upqnrotationor said-control member beyond said givenangular distance to effect move ment of said operating member axially to thus effect contact engagement between said contact bridging elementand said stationary contacts. 7

16. An electric switch comprising a support, stationary contacts carried by said support, an operating member mounted for rotational and axial movement on said support, contact bridging elements carried by said operating member, a rotatable control member, an over-running connection between saidcontrolmember-and operating member operableupon rotation of said controlmember through a givenzanglefrom a-neutral position to :rotate said operating :member =to1positionsaidcontact bridging elements in registrylfor engagement with said stationary contacts, cam means coupled to the control :member and aoperableon the operating member upon IQtH/tiOnIOf said control member through :a greater angle than said given angle to 'move said operating member axially to effect contact engagementbetween :said contact bridging elements and .stationary contacts, a latch operable in response to the axialmovement of-said operating 'memberifor latching said operating member against axial REFERENCES CITED The following references are of reeor'd in the file of this :patent:

UNITED STATES PATENTS Number a Name Date 1 $46,413 Brennan Feb ZO, 11 923 1,593,386 Byles July 20, 1926 

